From 08bc243195a8a6128f8aab28676cded5d7afd055 Mon Sep 17 00:00:00 2001 From: Mark Mitchell Date: Sat, 31 Oct 1998 13:44:46 -0700 Subject: [PATCH] c-common.c (c_get_alias_set): Allow all type-punning through unions. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit � * c-common.c (c_get_alias_set): Allow all type-punning through unions. Don't get confused about the type of a bit-field, despite the antics of build_modify_expr. From-SVN: r23481 --- gcc/c-common.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-) diff --git a/gcc/c-common.c b/gcc/c-common.c index c9023585f3c..f45b5662020 100644 --- a/gcc/c-common.c +++ b/gcc/c-common.c @@ -3135,6 +3135,7 @@ c_get_alias_set (t) tree t; { tree type; + tree u; if (t == error_mark_node) return 0; @@ -3155,22 +3156,18 @@ c_get_alias_set (t) the conservative assumption. */ return 0; - if ((TREE_CODE (t) == COMPONENT_REF - && TREE_CODE (TREE_TYPE (TREE_OPERAND (t, 0))) == UNION_TYPE) - /* Also permit punning when accessing an array which is a union - member. This makes the current sparc va_arg macro work, but may - not be otherwise necessary. */ - || (TREE_CODE (t) == ARRAY_REF - && TREE_CODE (TREE_OPERAND (t, 0)) == COMPONENT_REF - && (TREE_CODE (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 0), 0))) - == UNION_TYPE))) - /* Permit type-punning when accessing a union, provided the - access is directly through the union. For example, this code does - not permit taking the address of a union member and then - storing through it. Even the type-punning allowed here is a - GCC extension, albeit a common and useful one; the C standard - says that such accesses have implementation-defined behavior. */ - return 0; + /* Permit type-punning when accessing a union, provided the access + is directly through the union. For example, this code does not + permit taking the address of a union member and then storing + through it. Even the type-punning allowed here is a GCC + extension, albeit a common and useful one; the C standard says + that such accesses have implementation-defined behavior. */ + for (u = t; + TREE_CODE (u) == COMPONENT_REF || TREE_CODE (u) == ARRAY_REF; + u = TREE_OPERAND (u, 0)) + if (TREE_CODE (u) == COMPONENT_REF + && TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE) + return 0; if (TREE_CODE (t) == INDIRECT_REF) { @@ -3184,6 +3181,15 @@ c_get_alias_set (t) /* From here on, only the type matters. */ + if (TREE_CODE (t) == COMPONENT_REF + && DECL_BIT_FIELD_TYPE (TREE_OPERAND (t, 1))) + /* Since build_modify_expr calls get_unwidened for stores to + component references, the type of a bit field can be changed + from (say) `unsigned int : 16' to `unsigned short' or from + `enum E : 16' to `short'. We want the real type of the + bit-field in this case, not some the integral equivalent. */ + type = DECL_BIT_FIELD_TYPE (TREE_OPERAND (t, 1)); + if (TYPE_ALIAS_SET_KNOWN_P (type)) /* If we've already calculated the value, just return it. */ return TYPE_ALIAS_SET (type); -- 2.30.2